You must go to xplrcmn.viv and extract misctpage.fsh (this is the template used for the display of the eyes, mouth, headband and shoes ingame). Drop this into NFSHtool, a folder will be created, there you'll see 3 images and a index.fsh file. Open this file with Notepad, it contains the info of misctpage.fsh, and among other its size. Go to line 9, 256 128 is the normal size, you can put there any values being a multiply of these (i.e. 512 256). You'll also need to increase the parameters refering to BUFSZ, 96976 worked for me.
Now, resize the 3 images. Being 0000-2 the bigger, it must have the new size you introduced, 0000-1 needs half the size of 0000-2, and 0000-0 needs half the size 0000-1.
right click the index.fsh file, open with...NFSHTool. The new file will be created. With EAgraph import it back to xplrcmn.viv.
I would recomand to use 256 128, so the shoes will have a size of 256 256. ( a bigger size will turn blurry most of the shoes out there)
The only shoes, mouth, headbands and eyes that will work ingame will be the new sized ones, so there's a lot of work resizing parts of the plrcmn.fsh (only mouth, eyes and headband) and the whole shoes.fsh (this file can turn into a big one if every shoe doubles its size). The method is the same as for the misctpage.fsh
Maybe a dedictaded patcher would do the hard work and release these new parts of xplrcmn.viv